Catalytically sweetening of naphtha



April 3, 1956 s. B. swEETsi-:R ETAL 2,740,747

CATALYTICALLY SWEETENING OF NAPHTHA Filed Nov. 20, 1952 CATALYTICALLY SWEETENIN G OF NAPHTHA Sumner B. Sweetser, Cranford, Stanley 0. Bronson II, Mountainside, and Robert C. Morbeck, Fanwood, N. J assignors to Esso Research and Engineering Company, a corporation of Delaware Application November 20, 1952, Serial No. 321,653 3 Claims. (ci. 19e- 28) The present invention is concerned with an improved process for the manufacture of high quality hydrocarbon products boiling in the motor fuel boiling range. The invention is more particularly concerned with the production of a low sulfur, mercaptan-free, high octane number motor fuel having a good odor. In accordance with the present invention a hydrocarbon feed boiling in the motor fuel boiling range is treated in an initial zone with a catalyst selected from a particular class. Suitable catalysts are molybdenum oxide on alumina, cobalt molybdate on alumina, and mixtures of nickel and tungsten suldes. The treated product is passed to a secondary zone to remove hydrogen sulfide and nally processed in a tertiary zone utilizing caustic and air in order to remove the nal traces of mercaptan sulfur.

It is well known in the art to process hydrocarbon oils boiling in the motor fuel boiling range by various operations in order to either remove sulfur compounds or to convert sulfur compounds such as mercaptans to relatively innocuous sulfur disuliides. It is also known to treat motor fuel products boiling in the motor fuel boiling range with caustic in the presence of air for identical reasons. However, when treating a petroleum product containing mercaptans with caustic in the presence of air the mercaptans are converted to disuliides. These disuliides in the product are not entirely satisfactory since they adversely effect the response of the fuel to tetraethyl lead, with respect to octane number improvement. On the other hand, when'contacting a fuel containing mercaptans with a catalyst of the present invention, Vsubstantially all the mercaptans are removed. However, the product will not pass a doctor test.

The present invention is broadly concerned with the production of a high quality improved motor fuel which boils below about 430 F. It is more particularly con cerned with the sweetening of sour naphthas by an improved combination process comprising a catalytic sweetening step and an air sweetening step. In the catalytic sweetening step the oil is contacted with a catalyst selected from the class consisting of cobalt molybdate on alumina, molybdenum oxide on alumina, and a mixture of nickel and tungsten sulfide.

The process of the present invention may be more fully understood by reference to the drawing illustrating one embodiment of the same.

Referring specifically to the drawing, a hydrocarbon oil boiling in the range from about 100 to 430 F. is introduced into treating z'one 1 by means of line 2. In zone 1 the oil is contacted with a catalyst comprising about 5 to 15% molybdenum oxide on alumina. Temperatures are preferably in the range from about 400 F. to 700 F., while pressures are in the range from about 0 to 500 p. s. i. g. A preferred temperature is in the range from about 550 F. to 650 F., while the preferred pressure is in the range from about 50 to 250 p. s. i. g. The feed rates may vary appreciably, but desirable feed rates are from l to 16 volumes of feed per volume of catalyst per hour.

nited States Patent O 2,740,747 .Patented Apr. 3, 1956 vice The catalytically sweetened oil is removed from stage 1 by means of line 3. A small amount of caustic, as for example, from 2 to 4% of a 15 B. strength is added to line 3 by means of line 4. The oil and the caustic is passed through a mixing zone 5 and introduced into a settling zone 6. Spent caustic is segregated and removed by means of line 7.

The segregated oil is removed from zone 6 by means of line 8 and mixed with from 5 to 15% by volume, preferably with about 10% by volume of an 8 to 15 B. strength caustic solutionwhich is introduced lby means of line 9, and an inhibitor, as for example, of the phenylene-diamine type may be added by means of line 10. Air is introduced by means of line 11 and the entire mixture passed through a mixing zone 12.

The mixture is passed to settling zone 13, wherein spent caustic may be removed by means of line 14. The treated oil is separated by means of line 15 and passed to a storage zone 16 Where it is preferred the same remain in storage for a period from about 1 to 7 days. The treated oil substantially free of mercaptans and of a high quality sufficient to pass the doctor test is removed from zone 16 by means of line 17 and handled or further refined as desired.

The amount of caustic utilized in the air sweetening may vary appreciably, as for example, from 5 to 25% of caustic by volume based upon the oil. The strength of the caustic may also vary appreciably, as for example,y

A number of operations were conducted wherein a West Texas light virgin naphtha was catalytically sweetened in accordance with the present invention. The results of these operations are listed in the following table:

Table 1.-C0mbnaton catalytic plus air-caustic .sweetening of West Texas light virgin naphtha [L Catalytic sweetening; 600 F., 200 p. s. i. g., 10% MoO on alumina catalyst] Feed Rate, V./Hr./V Feed 4 8 16 Mercaptan Number-.. 41 0. 6 0. 7 1. 3 Sulfur, Wt. Percent 0.083 0.022 0. 024 0. 028 O. F. R. R. Octane Number:

Clear 69. 7 67. 6 69. 4 70. 1

+2 ce. TEL 80. 3 83. 9 82. 5 82. 1 Doctor Test l. DNP DNP DNP DNP Odor DNP Pass Pass DNP [IL .Air-caustic sweetening of above products shaken for 3 minutes with 10% of 15 B. caustic and left in contact with 9 volumes of air till sweet.)

Time to get Doctor Pass Product, Hours-..-. 1 30 30 1 1n the doctor test a small sample of the oil is shaken vigorously with a small amount of the doctor solution which consists of 15 B. caustic saturated with litharg'e. After shaking the sample with the doctor sclution a small amount of powdered sulfur is added to the mixture and shaking repeated. It no discoloration of the sulfur at the interface between the hydrocarbon and aqueous layers develops, the sample passes the doctor test. The doctor test is an indication of Whether or not the oil i-s completely free of mercaptans.

From the above tabulation, it is evident that catalytic sweetening of the West Texas light virgin naphtha with feed rates of 4 to 16 v./hr./v. reduces the mercaptan number of the feed from 4l to about l with a corre sponding removal of about 70% of the sulfurs. Simul` taneously the octane number of the product was improved 2 to 3 points on a leaded basis. In spite of the low mercaptan number of the products, they still did not pass a doctor test. The catalytically sweetened products were treated in a separatory funnel with 10% of 15 B. causticandy shaken incontact with air forv three minutes. The naphtha and aqueous layers were allowed to separate and samples of the naphtha withdrawn periodically fora doctor -testl The settledvr products becamedoctor sweetwithin a periodofA 1 to 30 hours.

Although air caustic sweetening is thus shown to be elective for removing small amounts of mercaptans from catalytically sweetened products, the air caustic sweetening process isv not suitable for treating the raw virgin feed with a mercaptan number as high as 4l since excessively severe treats and long periods of contact with air would be required inorder to obtain even a partial removal of rnercaptans.`

EXAMPLE`2 Other operations Vwereconducted whereina West Texas virgin naphtha was catalytically sweetened. The results of these tests are as follows:

Table II [Catalytic swectcniug of West Texas light virgin naphtha with CoMoO on alumina; 600 F., 200 p. s. i. g.]

Feed Rate, VJHL/V Feed 1. 7v 3. 8 7. 9 Mercaptan Nurnbor 41 0.6 0. 5 0. 8 Sulfur, Wt. Porcent 0. 083 0. 020 0. 023 0. 027 C. F. P.. R. Octane No Clear 60. 7 68. 6 69. 0 68. 6 +2 Cc. TEL 80. 3 82. 0 82. 0 S2. 0

The feed utilized in Examplel has also been catalytically sweetened with a cobalt molybdate catalyst. The results in the above table show that with a cobalt molybdate catalyst the extent of sweetening obtained was at least as good as with the catalyst which was used in Example 1.

EXAMPLE 3 F. Initial boiling point 120 10% distilled 149 50% distilled 225 90% distilled 334 Final 442 The results of these operations are illustrated in the following table:

Table III Operating Conditions:

Temperature, 1F 600 600 Feed Rate, V./Hr./V 7; 8 4. 0 Pressure, p. s. i. g 200 200 Feed In- Product Inspections: speetions Sulfur, Wt. Percent 0.143 109 091 Hcreaptan Numbc 21 0.7 0.8 Bromine Number 4. 3 4. 7 1. 1 C. F. R. R. Octane Number:

Clear 69. 4 70, 0 72. l +2 cc. TEL 79. 6 81. 8 84.0

The results presented in the above tabulation show that blends of virgin and cracked naphthas can be handled effectively by catalytic sweetening. However, the concentration of cracked stocks in the blend should not exceed about 25%. With the cracked stocks as with virgin feeds, mercaptans were substantially eliminated; sulfur was appreciably reduced and an increase in leaded octane number of the product obtained.

The present invention is concerned with the catalytic sweetening of petroleum oils boiling in the motor fuel boiling range. No hydrogen or other extraneous gas is added to the catalytic sweetening zone. The catalysts are selected from the class consisting of cobalt molybdate on alumina, molybdenum oxide on alumina and a mixture of nickel and tungsten sulfide. The amount of cobalt molybdate and molybdenum oxide utilized is in the range from about 5 to 15% by weight based upon the alumina.

Preferred temperatures are'in the rangefrom about 550 F. to 650' F., while preferred pressures are in the range from about 50 to 250 p. s. i. g.

What is claimed is:

1. Improved process for the complete removal of mercaptan compounds from petroleum oils boiling in the motor fuel boiling range which comprises contacting these oils with a catalyst selected from the class consisting of cobalt molybdate on alumina, molybdenum oxide on aluminaand a mixture of tungsten sulfide and nickel suliide at a pressure belowv about 500 p. s. i. g., a tempera tureY in the range from about 400 to 700 F., and in the absence of added hydrogen, removing the treated oil and separating hydrogen sulfide therefrom, thereafter contacting the oil with caustic in the presence of added air, whereby a doctor pass product is secured.

2. Process as deined byv claim l wherein the temperature is inthe range from about 525 to 625 F., and wherein the. pressure is inthe range from about to 225 p. s. i. g.

3. Processv as defined by claim 1 wherein the hydrogen sulde is removed by utilizing a relatively small amount of. caustic and wherein theY concentration of the caustic in the nal stage is in the range from 8 to 15 B.

References Cited inthe file of this patent UNITED STATES PATENTS 1,257,829 Evans Feb. 26, 1918 2,392,579 Cole Jan. 8, 1946 2,393,288 Byrns Jan. 22, 1946 2,413,312 Cole Dec. 31, 1946 2,413,945 Bolt Jan. 7, 1947 

1. IMPROVED PROCESS FOR THE COMPLETE REMOVAL OF MERCAPTAN COMPOUNDS FROM PETROLEUM OILS BOILING IN THE MOTOR FUEL BOILING RANGE WHICH COMPRISES CONTACTING THESE OILS WITH A CATALYST SELECTED FROM THE CLASS CONSISTING OF COBALT MOLYBDATE ON ALUMINA, MOLYBDENUM OXIDE ON ALUMINA AND A MIXTURE OF TUNGSTEN SULFIDE AND NICKEL SULFIDE AT A PRESSURE BELOW ABOUT 500 P. S. I. G., A TEMPERATURE IN THE RANGE FROM ABOUT 400 TO 700* F., AND IN THE ABSENCE OF ADDED HYDROGEN, REMOVING THE TREATED OIL AND SEPARATING HYDROGEN SULFIDE THEREFROM, THEREAFTER CONTACTING THE OIL WITH CAUSTIC IN THE PRESENCE OF ADDED AIR, WHEREBY A DOCTOR PASS PRODUCT IS SECURED. 